Fns now annotated with invoke urls, as per triggers (#1172)

Clone of the trigger work to inject invoke urls into the annotations
on a fn when it is returned from the server.

Small changes to trigges code following code review of the fn code.

api/server/server_test.go

@@ -38,6 +38,7 @@ func testServer(ds models.Datastore, mq models.MessageQueue, logDB models.LogSto
 		WithAgent(rnr),
 		WithType(nodeType),
 		WithTriggerAnnotator(NewRequestBasedTriggerAnnotator()),
+		WithFnAnnotator(NewRequestBasedFnAnnotator()),
 	)...)
 }